Jon, I'm sorry I wasn't clear I meant why put such an expensive DRO on an old machine when a cheaper one will be just as good. I built two of the Shuma Tech DRO's for about $250 each including scales and they are accurate to .0005". I'm like you and can barely turn the screw just enough to get .001" with out overtravel because of worn screws and nuts. My ways are still nice and flat and I do long work on the manual mill.
John On 2 Feb 2008 at 14:43, [EMAIL PROTECTED] wrote: > John Thornton wrote: > > I just wonder why you want to put such a nice DRO on a worn out old > > manual mill that needs the ways scraped and the screws are worn out? > Hate to argue, but the differential wear in the screws makes it > totally impossible to make anything with better than 1/8" > accuracy using the dials on the handwheels. With a DRO or any > other direct measuring scheme, you CAN make FAR more accurate > parts. Even a dial caliper bolted to the slides will work. > The differential wear on the screws can easily be more than one > order of magnitude worse than any worn spot in the ways. > You will not be able to > > make an accurate part to the abilities of your DRO if the table > > won't stay where you put it and your Z is always changing because > > your table moves up and down as you move X and Y because the ways > > are worn. > I have a 1938 Bridgeport with all this sort of way wear, but I > can make parts of substantial size to within .001" tolerance > with little difficulty. With the original Acme screws, I was > lucky to get within .025" of where I wanted to be. I put an > ancient Bridgeport optical measuring system (glass reflective > scales and rear-projection magnifier boxes) on it in 1995 or so, > and suddenly I could make a box with holes and a cover with > matching holes, and didn;t have to spend a day filing out the > holes to match! Wow! > > Jon ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
